The present invention is related to binocular vision and treatment of the eye.
People like to see. However, the eye can have defects that may result in less than ideal vision in at least some instances. For example, refractive errors of the eye can cause uncorrected vision to degrade. Refractive errors of the eye include nearsightedness, also referred to as myopia, farsightedness, also referred to as hyperopia, and astigmatism. These refractive errors can be treated with combinations of spherical lenses and cylindrical lenses, and the refractive prescription used to treat an eye, sometimes referred to as a refraction, can include a spherical optical power, a cylinder optical power and an axis of the cylinder. An example of a prior device that can be used to test vision with spherical and cylindrical lenses is the phoropter. The phoropter may contain different lenses used to measure refraction of the eye during sight testing and in at least some instances may be used to measure an individual's refractive error of both eyes to determine the eyeglass prescription.
Correction of the refractive error of the eye with spherical and cylindrical lenses may not fully correct at least some of the optical errors of the eye and can leave a patient with less than ideal correction in at least some instances. For example, the eye can have aberrations such as spherical aberration and coma that limit the effectiveness the refractive prescription that may be used with treatments such as spectacles and contact lenses. Also, although optical instruments such as microscopes, cameras, binoculars, telescopes and long range sighting (hereinafter “LRS”) may correct for at least some optical errors of eye such as sphere, uncorrected spherical aberration and coma can limit vision with such optical instruments in at least some instances. As the eye ages, the ability of the eye to focus decreases such that people with good distance vision may wear corrective reading glasses to read. This age related decreased accommodation of the eye can be referred to as presbyopia.
The human eye can perceive color and the light used in many viewing situations includes more than one color of light. Natural light comprises polychromatic light having several colors. Although the human eye can perceive colors such as the primary colors red, blue and green, the human eye has chromatic aberration such that vision can be degraded when more than one color is viewed. Artificial light in many situations can include polychromatic light, for example florescent lights and incandescent lights. As chromatic aberration can affect measurements of the aberrations of the eye, many devices that measure aberrations of the eye rely on monochromatic light having only one wavelength of light or a narrow range of wavelengths.
Measurement of the monochromatic aberrations of the eye with wavefront sensors can allow for the correction at least some of the monochromatic optical errors of the eye. The monochromatic aberrations measured with wavefront sensors are sometimes referred to as wavefront elevation maps. While the wavefront elevation maps may show monochromatic optical errors of the eye as an elevation map of optical path distance from a reference plane, it can be helpful to decompose the wavefront map into orthogonal aberration terms, for example Zernike polynomials. With the polynomial approach, the second order terms correspond to sphere and cylinder of an eyeglass prescription. The sphere of an eyeglass prescription corresponds to the second order defocus term and the refractive cylinder of an eyeglass prescription corresponds to the second order astigmatism terms. The terms above second order of the polynomial decomposition can be referred to as high order aberrations.
Wavefront sensor measurements have been used to treat optical errors of the eye such as high order aberrations. For example, a laser can be programmed to ablate tissue of the eye based on the wavefront sensor measurement. However, at least some vision correction treatments such as refractive surgery, contact lenses, and intraocular lenses (hereinafter “IOLs”) can induce high order aberrations of the eye. For example, the pupil may be larger than the proposed optical correction at night with some patients, such that at least some aberrations may result with night vision following treatment. It would be helpful to determine the effect of aberrations on vision and test the response of the patient to a treatment prior to the patient receiving treatment, such that the potential satisfaction of the patient with a proposed treatment can be determined. For example with laser eye surgery, it may be helpful to test the proposed treatment of the eye prior to ablation with the laser beam. Also, the treatment of presbyopia can include a multifocal lens that may induce aberrations that increase the depth of field of the eye, and it may be helpful to test the vision of the patient prior to treatment with the multifocal lens, for example.
At least some of the prior devices used to measure and test vision with aberrations prior to treatment such as surgery can perform less than ideally in at least some instances. For example, at least some of the prior devices that measure and correct monochromatic aberrations are not well suited for the evaluation of vision with polychromatic light. As normal vision can include polychromatic light, testing vision with monochromatic light may not provide a realistic assessment of vision with polychromatic light in at least some instances. Also, at least some of the prior devices determine vision with monocular viewing, and normal vision can be binocular such that testing a proposed treatment with monocular vision can be less than ideal.
Although some of the prior systems have tested binocular vision with aberration correction, these systems have produced less than ideal results in at least some instances. For example, at least some of the prior systems have relied on the patient viewing a target inside the apparatus in an artificial viewing environment that may not accurately assess vision. Also people can often be aware of their surroundings, and viewing an artificial target positioned inside the apparatus may result in the patient perceiving that he or she is looking inside the apparatus rather than at a remote target, such that the measurements can be less than ideal in at least some instances. Also, at least some of the prior binocular viewing systems may have flat target and in at least some instances may not present a three dimensional viewing environment for the patient to test vision as would occur normal vision in a room.
For the above reasons, it would be desirable to provide improved methods and apparatus for the determination of vision with aberration correction. Ideally such methods and apparatus would overcome at least some of the above mentioned deficiencies of the prior devices and provide an assessment binocular vision with aberration correction in a normal viewing environment that allows the patient to view his or her surroundings in polychromatic light with both near and far vision.